Liquation of metals



LIQUATION OF METALS Filed Feb. 5, 1952 EZI- @Maggy/g ATTORNEY Patented Apr. l2, 1932 UNITED :STATE-.svPArlzu'r vor-'l-ICE JESSE 0. .'BETIERTGI', 0l' IETUCEM NEW JERSEY, ASSIGNOB TOAmICAN Smil'- IN'G AND BEIFINING COMIAY, OF NEW YORK, 1 1'. Y., A GOBPOBA'LIGN'` 0F ANEW' Lmrra'rrorr or mars amilmaunv area February s, 193s. serial un. 591,197.

This invention relates to the refining of metals, and more particularly to the removal and recovery of bismuth from various metals in which it may be present as an impurlty,

i 5 as for example, from lead bullion.

The present invention provides .forremoving the bismuth from the lead bulhon'in combination with certain other impurities in a, complex dross vand then treating the dross by 10 liquation for the selective removal of the various metals therefrom.

The invention further consists in the new and novel features of operation and the new and original arrangements and combmatlons of stepsin the process'hereinafter described thereof, in which the igureis a flow sheetV illustrating the present process.

In the following description and 1n the claims the various steps in the process and the o details comprising the invention will be identiied by specific names for convenience but they are intended to be as generic in their` application as theartwill permit.

The present process is carried out for the vremoval and recovery of bismuth from lead bullion by suitably treating the bullion as by the addition of zinc to remove the silver therefrom as a zinc-silver dross, and thereafter applying to the bath of molten lead a suitable reagent, such as an alkali earth metal, preferably alloyed with lead or lead with some zinc to form a dross containing the bismuth,-

the alkali earth metal, zinc and lead. y This dross is then removed from the bath andmelted under a suitable cover slag after which the lead is removed by liquation and the alkaliV 1 be returned tothe bathras above described.

earth metal and bismuth are separated from the cover slag by selective tapping and are treated for the recovery of the metal values.

More specifically the invention may be carried out by adding to the lead bullion zinc and blocks containing some silver from previous reaction. A zinc-silver dross then forms ou. Y

the surface of the bath which may be pressed to largely separate the lead therefrom and may be removed from the bath. The dross is 'then treated in retorts wherein the silver is recovered in the usual manner.

After the dross has been removed zinc plates may be added and the bath gradually .allowed to cool toa temperature of 660 F. whlle further quantities of dross are formed and simultaneously removed. This dross may be cast into blocks and returned to the bullion as above mentioned as a source of zinc in the desilverizing step. Y

Thereupon a suitable alkali earth metal, such for example .as calcium, preferably in the form of a lead alloy or in the form of a lead-zinc alloy is added to the bath. Ait the same time blocks and rims, together with lead and zinc containing all of the alkaline lnetal, plus silverv from subsequent"I steps of the process, to be hereinafter described, are added to the bath. The bath is then vigorously stirred, preferably by a mechanical stirrer,

and at this stage of the operation the bath is carefully held at a temperature of 640 to 660 F. at which temperatures oxidation of the calcium is almost completely prevented and alsoa much higher ratio of bismuth extraction per pound of calcium is secured. The Vresulting dross which comprises bismuth, calcium, zinc, lead and some silver may then be pressed, if desired, to reduce the lead content and removed from the bath and .further treated for the recovery of the metal values in the manner to'be described.

Thereafter, the bath may be cooled to about 625 'F. and blocks may be formed from the resulting dross. Rims may be also formed adjacent the sides of the container as the metal solidiies. These blocks and rimsv may perature of 670 F. to 750 and adding a zinc chloride cover thereto in suliicient uantity to -completely cover the top of the ath.

Chlorine is introduced into the bath beneath this cover and unites with the zinc and calcium to form slags of zinc chloride and calcium chloride. .NThe first slag formed will contain all of the calcium as calcium chloride and some of the' zinc as zinc chloride. This may be removed and used in any suitable manner or may be discarded. The final slag which is formed after calcium is removed represents the normal zinc chloride salt and l maybe .used as such.' The lead bath after the removal of the above impurities may be further refined in any well known manner.

The bismuth-calcium-zinc-lead-silver dross,-

above mentioned which has been removed from the lead bath is then heated under a cover slag of calcium chloride together with sodium chloride which has preferably been dehydrated. One method of carrying out this stepis to heat the calcium chloride mixed with sodium chloride in a suitable kettle to a ltemperature of 10001300 F.,vadd the above mentioned dross and heat the mixture to a termperature suflicient to substantially l asmall amount of bismuth and calcium is then tapped and returned to the lead bullion, together with the calcium-lead alloy ahead of the debismuthizing step as previously described. Y

The kettle containing the slag and the calcium-bismuth-zinc layer is thenreheated to a temperature sufficient to substantially melt the same, as for example, 1000 F. to 1800 F.

and the calcium-bismuth-zinc layer is tapped and suitably treated to separate and recover the calcium, bismuth and zinc therefrom. This layer contains a relatively small amount of lead, for example 10 to 30%, and calcium in amounts of approximately one-half to onethird of the bismuth content.

The moltenl slag of calcium chloride and sodium chloride which may contain small quantities of calcium oxide is then tapped or otherwise removed from the kettle and sent to a suitable recovery apparatus or discarded.

- By means of my improved process the removal of bismuth is carried out in combination withthe usual desilverizing steps, thereby saving time and labor involved in twice coolin the bath almost to the melting point of le and also saving the expense and labor involved in re-heating the kettle to a relatively high temperature intermediate of two i y cooling steps.

` Not only is the bismuth removed almost-k completely, butra substantial amount of zinc usually remaining-in lead bullion after the desilverizin step is also removed and may be recovere as metallic zinc with the resultving economy in the cost of the operation.

bath and duplication of o erations is thus avoided. The process has en described as carried out by the use of a calcium-lead alloy or the use of 'a calcium-lead-z-inc alloy for the removal of bismuth but it is to be understood that other alkali earth metals including magnesium may be substituted for the calcium and may be removed from the" lead bath and from the bismuth dross in a corresponding manner.

Although certain novel features of the invention have been 'shown and described and are pointed out in theannexed claims, it will be understood that various omissions, substitutions` and changes in the several ste s of the process and in its operation may e made by those skilled in the art without departing from the spirit of the invention.

The present application is a continuation in part of Betterton, Serial Number 492,852, filed November 1, 1930.

What is claimed is:

1. The process of removing impurities, such as silver, zinc and,Y bismuth, from lead bullion which comprises removing silver as a zinc-silver dross, removing the bismuth and a portion of the residual zin'c by the addition of an alkali earth metal as a dross, melting said dross under a cover slag, se arating the lead therefrom by liquation an separating the bismuth and alkali earth metal from the cover slag by selective tapping.

2. The process of removing bismuth from lead which comprises adding to a bath of molten lead a reagent yielding an alkali earth metal within the body of the molten lead in a condition capable of forming a dross with said bismuth, removing said dross and melting the same under a chloride slag, separating the lead from said dross by liquation and returning the lead to theA original lead bath ahead of the debismnthizing step, heating the liquate to cause the slag and the bismuth to separate into different layers-and selectively removing said layers.

3. The process of recovering bismuth from lead containing bismuth as an impurity which comprises adding a calcium alloy to a bath of molten lead under conditions suitable for the formation of a calcium-bismuthlead dross, removing said dross from the bath, melt-ing the same under a chloride slag, separating the lead from' the dross by liquation, causing the calcium and bismuth to separate from the slag as a distinct layer and removing said layer.

4. The process of recovering bismuth from a mixture containing bismuth, calcium and lead which comprises melting said mixture under a chloride slag, cooling to a temperature at which the slag and a layer of calcium and bismuth separate from the lead and solidify, removing the molten lead therefrom, reheating to completely fuse the slag, calcium and bismuth and to cause them to maintain distinct layers and separately removing said layers by selective tapping.

5. The process of separating bismuth, calcium and lead from mixtures containing these metals which comprises melting said mixture under a slag of calcium chloride and sodium chloride, heating 'the mixture to a temperature at which all of the constituents are molten, cooling the mixture to a temperature at which the slag and the calcium and bismuth solidify while the lead remains molten, removing the molten lead, reheating the mixture to a temperature at which all of the remaining constituents are molten, allowing said constituents to separate in two layers, one layer containing the calcium chloride and sodium chloride, and the other layer containing the calcium and bismuth, separating said layers and treating the calcium-bismuth layer for the recovery of bismuth.

6. The process of separating bismuth, calcium and lead from mixtures thereof Which comprises heating said mixture under a layer of calcium chloride and sodium chloride to a temperature of 10000 F. to 13000 F., cooling the mixture to a temperature of 8000 F. to 9000 F. whereby the lead is separated by liquatlon, removing the molten lead, reheating the remaining constituents to a temperature of 1000 0 F. to 18000 F. whereby the calcium chloride and sodium chloride separate as one layer and the calcium and bismuth as a second layer,removing the layer of calcium and bismuth and treating the same for the recovery of said metals.

7. The process of removing impurities, such as bismuth and silver', from lead which, comprises adding zinc to a bath of molten lead and removing the resultant zinc-silver dross, adding an alkali earth metal to said bath and removing the resultant dross containing bismutb, treating the bath under a chloride slag with chlorine gas to remove the zinc and alkali earth metal as chlorides and treating the bismuth dross Iby melting said dross under a chloride slag, liquating the same to separate lead, returning the lead so separated to the original bath ahead of the debismuthizing step, causing the bismuth and alkali earth metal to separate as a distinct layer from the chloride slag and separately removing said layer and treatin the same for the recovery of bismuth there rom.

8. The process of recovering bismuth from a lead bath containing this element as an impurity which comprises adding calcium to said bath and allowing a bismuth-calclumlead dross to form, removing said dross, treating' the bath with chlorine under conditions favorable to the formation of a calcium chloride slag, whereby the calcium is removed therefrom, separately treatingthe bismuth dross by melting under a chloride slag, separating the lead therefrom by liquatlon and separating the calcium and blsmuth fromsald slag by heating the mixture to substantially liquefy the Various constituents, wherebythe calcium and bismuth separate as a dlstmct layer. p

9. The process of removing bismuth from lead containing the same as an impurlty which comprises treating a bath of said lead with a reagent yielding an alkali earth metal within the body of the molten lead in a condition capable of forming a dross containing said bismuth, removing the dross and melting the same under a chloride slag, separating the lead from said dross by liquation and v returning the lead to the origina-1 bath, and separating the bismuth from the slag by heating the mixture to a. temperature at which the Various constituents become liquid, whereby the lslag' forms a layer above the blsmuth and may be mechanically separated therefrom.

10. The process of recovering bismuth from a lead bath containing the same as an impurity which comprises treating said bath with a reagent yielding an alkali earth metal within the body of the molten lead in a condition capable of forming a. dross containing` bismuth, removing said dross from the bath, melting said dross under a cover slag and cooling to a temperature at which the slag and the bismuth solidify and the lead remains molten, removing the molten lead and returning the same to the original bath, reheating the dross to a temperature at which all of the constituents become molten, allowing the bismuth to separate as a distinct layer from the slag and mechanically separating said layers.

In testimony whereof I have hereunto set m hand.

`y JESSE O. BETTERTON. 

